Enhanced In Situ Anaerobic Bioremediation of Fuel-Contaminated Ground Water

Site Name:

Naval Weapons Station Seal Beach

Location:

Southern CA

Period ofOperation:

9/97- 10/98

CleanupType:

Field demonstration

Technology:In Situ Bioremediation
- Demonstration used one extraction and three injection wells (three zones of 180 m3 each)
- Extraction rate 4.5 L/min; injection 1.5 L/min/well
- Electron acceptors varied by zone - one zone augmented with sulfate, one with sulfate and nitrate, one with none; three rounds of augmentations performed
- Sampling performed with automated system

Regulatory Requirements/Cleanup Goals:
- Demonstrate the technical viability of the technology to treat petroleum hydrocarbons and to stimulate biodegradation of BTEX with nitrate and sulfate
- No specific cleanup goals were identified

Results:- Concentrations of BTEX compounds were reduced, with toluene preferentially degraded
- Ethylbenzene and m+p-xylene degradation stimulated by nitrate, with concentrations reduced from 250 to <10 ug/L for ethylbenzene and from 500 to <20 ug/L for xylenes
- O-xylene degradation stimulated by sulfate, with concentration reduced from >400 to <10 ug/L
- Benzene removal was mostly due to flushing rather than biodegradation

Cost Factors:- Demonstration costs were $875,000, including equipment, labor, laboratory supplies, travel, and overhead; >9,000 samples were collected
- Projected present value costs for a full-scale bioremediation application were $1,085,000, or $4,340/gallon of fuel recovered, compared with similar costs for pump and treat of $1,530,000, or $6,120/gallon of fuel recovered

Description:In 1984, a fuel leak was discovered at the Naval Weapons Station (NWS) Seal Beach when a steel tank was replaced with fiberglass tanks. NWS Seal Beach is located in southern California between Long Beach and Huntington Beach. About 5,800 gallons of fuel had leaked and migrated to the groundwater and was a concern for its potential effects on a local wildlife refuge.

A demonstration of in situ bioremediation was performed in a portion of the contaminated area of this site. The demonstration evaluated the performance of various concentrations of sulfate and nitrate in three zones between one extraction well and three injection wells. The results showed that concentrations of BTEX compounds were reduced, with toluene preferentially degraded. Ethylbenzene and xylenes also were degraded, but benzene was found to be removed mostly by flushing. Projected full-scale costs for in situ bioremediation were found to be approximately 30% less than for pump and treat. Lessons learned included the effect of BTEX compounds in a non-aqueous phase, the demand of non-BTEX fuel hydrocarbons on sulfate and nitrate, and the role of sulfate and nitrate as terminal electron acceptors.